Software-as-a-Service (SaaS) is a delivery model whose basic idea is to provide applications to the customer on demand over the Internet. In contrast to similar but older approaches, SaaS promotes multi-tenancy as a tool to exploit economies of scale. This means that a single instance of an application serves multiple customers. The customers, who are also called tenants, are for example companies, clubs or private persons that signed up to use the application. Even though multiple customers use the same instance each of them has the impression that the instance is designated only to them. This is archived by isolating the tenants' data from each other. In contrast to single-tenancy, multi-tenancy hosts a plurality of tenants on the same instance.
However, one of the major drawbacks of multi-tenancy applications is the customers' hesitation of sharing infrastructure, application code, or data with other tenants. This is due to the fact that customers are afraid that other tenants might access their data due to a system error, malfunction, or destructive action. So far this problem has only been tackled by implementing and improving the isolation of tenants on a single instance.